Officials in Russia's northern city of Arkhangelsk have acknowledged that one of the doctors who helped treat victims of a recent mysterious explosion at a military test site was found to have a radioactive isotope in his body.

Despite the doctor's exposure to patients from an area where a short-term radiation spike was recorded, the local health ministry blamed the trace amounts of the isotope on bad seafood.

"Cesium-137... has the feature of accumulating in fish, mushrooms, lichens, algae," the statement posted on the local government's website reads.

According to the local ministry of health, more than 110 first responders were examined. Some were even taken to Moscow's specialised facilities for additional screening, shedding new light on the scale of the incident.

Tatyana Rusinova, the acting minister of health in Arkhangelsk, said that, apart from the doctor with cesium-137, "No radioactive contamination of clothing or body surfaces was detected".

Investigative newspaper Novaya Gazeta later reported that two of the workers died from radiation poisoning.

Reports claiming that dozens of medical workers were exposed to radiation have been circulating for a while. Several independent news outlets published anonymous accounts of doctors angered by the fact they were not warned about radiation and lacked basic protective gear.

The Kremlin swatted the reports away, with President Vladimir Putin's spokesman Dmitry Peskov questioning the veracity of the sources.

"I'm not aware of it, I do not know what doctors you are talking about. It is necessary to know specifically what doctors are mentioned, who they are," Mr Peskov said in a conference call with reporters on Thursday.

When pressed to comment further, Mr Peskov accused the media of attempting to "distort reality".

"Have you not tried to look at the situation from a different side?" Mr Peskov said.

"The way the situation unfolds makes it seem like somebody intentionally wants to escalate the media coverage around this, distort reality and present the situation as if there are reasons to be worried about the danger."

But one of the doctors employed at Arkhangelsk regional hospital – Igor Semin, a cardiovascular surgeon – came out publicly, slamming the authorities for putting the lives of his colleagues at risk.

"Many were let down: young guys, the oldest of whom was 31 years old and collapsed from radiation in a day, the population of Severodvinsk... doctors, my colleagues who found themselves in front of the victims with empty hands, not even a respirator," Mr Semin wrote on his page on a social networking site called Vkontakte.

"No one said anything, did not warn anybody – they threw them under a bus and let us sort it out."